1. Field of the Invention
The invention generally relates to a network searching method adapted to a mobile electronic device, and more particularly, to a network searching method adapted to a mobile electronic device in a no service state.
2. Description of Related Art
Generally, when there is no service available, a mobile electronic device (for example, a cell phone or a smart phone) keeps performing a network searching operation until it finds and connects to an available network. As a result, the battery power of the mobile electronic device is quickly consumed. For example, one may leave his or her cell phone in the car and park the car in the basement. As a result, the cell phone remains in a no service state for a very long time therefore cannot register with any available network. Based on the existing technique, the cell phone keeps searching for an available network at regular intervals until the battery power is exhausted.
FIG. 1 is a networking searching timing diagram of a conventional mobile electronic device in a no service state. Referring to FIG. 1, the abscissa represents time in unit of second. The period from time t1 to time t2 is referred to as a search interval I1. During the search interval I1, the mobile electronic device performs a network searching operation. In the present embodiment, the search interval I1 is, for example, 5 seconds. The period from time t2 to time t3 is referred to as a sleep interval I2. If the mobile electronic device does not find any available network, it stops searching for any network during the sleep interval. In the present embodiment, the sleep interval I2 is, for example, 30 seconds. The sleep interval is followed by another search interval, during which the mobile electronic device performs another network searching operation. If the mobile electronic device cannot find any available network, it repeatedly performs and stops the network searching operation until an available network is found or the battery power of the mobile electronic device is exhausted.
In another existing network searching method, the sleep interval is set to a variable value, and the longer the mobile electronic device remains in the no service state, the longer the sleep interval is. Such a design contradicts the communication protocol compatibility test specified by the 3rd Generation Partnership Project (3GPP). Besides, when the mobile electronic device moves to a valid network coverage area, it may not be able to resume the network searching operation due to the overlong sleep interval. As a result, an unpleasant experience is brought to the end user.